A cosmic vacuum cleaner “made in Germany”

There is a German-built instrument on board the Cassini space probe: the “Cosmic Dust Analyzer” (CDA). DLR's institutes in Berlin-Adlershof and Braunschweig helped to develop and build it, and to test its spaceworthiness.

This complex instrument allows simultaneous analysis of the electric charge, speed, flight direction, mass, and chemical composition of dust particles in the interplanetary space, especially near Jupiter and Saturn. Dr Ralf Srama of the Max Planck Institute for Nuclear Physics (Max-Planck-Institut für Kernphysik) in Heidelberg is the lead scientist for the experiment.

The main goal of the CDA measurements is to study Saturn’s enormous dust rings. It became clear, for instance, that Saturn’s E ring – with its diameter of 300 000 kilometres the largest planetary ring of the Solar System – is much larger than assumed before. This discovery is incompatible with our existing understanding of the origin and development of this enormous ring.

Together with the ring particles, many icy moons orbit around Saturn, they are both the sources of the ring particles as well as sometimes the “sinks”, as ring particles get deposited on their surfaces.

The icy moon Enceladus had already very early on been identified as the main source of the rings. However, the scientists received a big surprise when, during a close flyby of this moon, they identified a concentrated jet of dust and gas, which escapes from cracks in the moon’s south polar region. The combined observations of the Cassini instruments provide convincing evidence of the presence of liquid water in cavities under the cracks, which under high pressure is ejected into space through these “cryovolcanoes”.